Semiconductor device, and method of manufacturing semiconductor device

Abstract

A semiconductor device comprises: an n-type semiconductor substrate; a p-type anode region formed in the semiconductor substrate on its front surface side; an n-type field stop region formed in the semiconductor substrate on its rear surface side with protons as a donor; and an n-type cathode region formed in the semiconductor substrate to be closer to its rear surface than the field stop region is, wherein a concentration distribution of the donor in the field stop region in its depth direction has a first peak, and a second peak that is closer to the rear surface of the semiconductor substrate than the first peak is, and has a concentration lower than that of the first peak, and a carrier lifetime in at least a partial region between the anode region and the cathode region is longer than carrier lifetimes in the anode region.

What is claimed is: 
     
       1. A semiconductor device comprising:
 an n-type semiconductor substrate; 
 a p-type anode region formed in the semiconductor substrate on its front surface side; 
 an n-type field stop region formed in the semiconductor substrate on its rear surface side with protons as a donor; and 
 an n-type cathode region formed in the semiconductor substrate to be closer to its rear surface than the field stop region is, wherein 
 a concentration distribution of the donor in the field stop region in its depth direction has a first peak, and a second peak that is closer to the rear surface of the semiconductor substrate than the first peak is, and has a concentration lower than that of the first peak, 
 a carrier lifetime in at least a partial region including the first peak is longer than a carrier lifetime in the anode region, 
 a carrier lifetime at a depth position at which the concentration distribution of the donor exhibits the first peak is longer than the carrier lifetime in the anode region, 
 the concentration distribution of the donor in the field stop region in its depth direction has a plurality of peaks, 
 the first peak is a peak closest to the front surface of the semiconductor substrate among the plurality of peaks, and 
 the region that has a carrier lifetime longer than that in the anode region extends toward the front surface side of the semiconductor substrate past a position at which the concentration distribution of the donor exhibits the first peak. 
 
     
     
       2. The semiconductor device according to  claim 1 , wherein the first peak is at a position corresponding to an end portion of a depletion layer, on the rear surface side of the semiconductor substrate, that expands from a boundary between the anode region and an n-type region of the semiconductor substrate when an inter-electrode voltage of an anode and a cathode at the time of reverse recovery of the semiconductor device becomes a half value of an applied voltage at the time of reverse recovery. 
     
     
       3. The semiconductor device according to  claim 1 , wherein a local lifetime killer that shortens the carrier lifetime is provided on the rear surface side of the semiconductor substrate. 
     
     
       4. The semiconductor device according to  claim 3 , wherein a region where the local lifetime killer is present is formed at a position that does not contact a depletion layer that expands from a boundary between the anode region and an n-type region of the semiconductor substrate when a rated reverse voltage of the semiconductor device is applied. 
     
     
       5. The semiconductor device according to  claim 3 , wherein an injection amount of the local lifetime killer is 1/300 or more of an injection amount of the protons that correspond to a peak of the concentration distribution of the donor closest to the rear surface of the semiconductor substrate. 
     
     
       6. The semiconductor device according to  claim 1 , wherein the carrier lifetime in at least a partial region between the anode region and the cathode region is longer than a carrier lifetime in the cathode region. 
     
     
       7. The semiconductor device according to  claim 6 , wherein a carrier lifetime at a depth position at which the concentration distribution of the donor exhibits the first peak is longer than the carrier lifetime in the cathode region. 
     
     
       8. The semiconductor device according to  claim 1 , wherein the region that has a carrier lifetime longer than that of the anode region extends toward the front surface side of the semiconductor substrate past, by 30 to 40 μm, a position at which the concentration distribution of the donor exhibits the first peak. 
     
     
       9. The semiconductor device according to  claim 1 , wherein a local lifetime killer that shortens the carrier lifetime is provided in the region that: extends toward the front surface side of the semiconductor substrate past a position at which the concentration distribution of the donor exhibits the first peak; and has a carrier lifetime longer than that of the anode region. 
     
     
       10. The semiconductor device according to  claim 1 , wherein a carrier lifetime at a depth position at which the concentration distribution of the donor exhibits the first peak is extended toward the front surface side of the semiconductor substrate from the first peak. 
     
     
       11. The semiconductor device according to  claim 1 , wherein a carrier lifetime at a depth position at which the concentration distribution of the donor exhibits the first peak is longer than the carrier lifetime in an entire portion of the anode region and the carrier lifetime in an entire portion of the cathode region. 
     
     
       12. The semiconductor device according to  claim 1 , wherein a carrier lifetime at a depth position at which the concentration distribution of the donor exhibits the first peak is longer than a longest carrier lifetime in the anode region and a longest carrier lifetime in the cathode region. 
     
     
       13. The semiconductor device according to  claim 1 , wherein
 the semiconductor substrate includes a drift region, 
 the concentration in the field stop region is higher than the concentration in the drift region, 
 the concentration in the cathode region is higher than the concentration in the field stop region, 
 the concentration in the anode region is higher than the concentration in the drift region, and 
 a carrier lifetime at a depth position at which the concentration distribution of the donor exhibits the first peak is longer than the carrier lifetime in the anode region and the carrier lifetime in the cathode region.